The interactive element select must not
appear as a descendant of the a element.

The interactive element select must not
appear as a descendant of the button element.

Any select element descendant of a label element
with a for attribute must have an
ID value that matches that for attribute.

The select element cannot have more than one
selected option element descendant unless the
multiple attribute is specified.

A select element with
a required attribute and without
a multiple attribute, and whose
size is “1”, must have a child
option element.

The first child option element
of a select element with
a required attribute and without
a multiple attribute, and whose
size is “1”, must have either an
empty value attribute, or must
have no text content.